Hypercapnic ventilation during exercise: effects of exercise methods and inhalation techniques.

The effect of exercise on the ventilatory response to inhaled CO2 is uncertain because previous studies using different techniques have come to different conclusions. We undertook to resolve this problem by using multiple techniques and confining our study to a uniform level of mild exercise (VO2 = 10 ml/kg min). One group of subjects exercised on a treadmill and was tested with both rebreathing and steady-state CO2 methods. A second group exercised on a bicycle while using the rebreathing method. We found that the ventilatory response to CO2 was unchanged by mild exercise, regardless of the method used for CO2 inhalation or the technique used for exercise. These results indicate that under controlled conditions mild exercise does not produce any change in ventilatory sensitivity to CO2.